I have a few MP3 podcasts that I transfered from my PC ostensibly to the Podcast folder on my Sansa Fuze ClipZip. Unfortunately, when I try to access through the player, the files show up under the Music section and not the in the Books/Podcast section. That means the podcasts don’t automatically book mark.
I believe you have to make sure the Genre field in the ID3 tag indicates Podcast. MP3Tag is the most popular, free, dedicated tagging program.